Footwear Heel Design

ABSTRACT

A design of heel of footwear which reproduces the ground contacting portion, or minimally the key elements of the ground contacting portion of the heel of the wearer in shape and placement in relation to the foot and function. That is a shape of heel in the footwear which does not imbalance the natural functions and leverage of the foot in bipedal locomotion through addition of material outside the confines of the shape and measurements of the wearer&#39;s own heel in the sagittal plane. This design of heel will afford the wearer the grace, smoothness and ease of stride enjoyed while barefoot. The wearer of a shoe with such a shape of heel will not suffer from shocks and strains to the foot and supporting members caused by the shape of the shoeheel. These being the types of shocks and strains contributing largely to shin splints and plantar fasciitis and attendant pathologies.

Footwear heel designed to prevent additional forces acting against thewearer's heel caused by the footwear. The intention of the design beingto alleviate shin splints, plantar fasciitis and associated medicalproblems caused or worsened by said additional forces and to promoteease of gait and grace in heel and toe walking/running, that is bipedallocomotion wherein the strikepoint of the leading foot is the heel.

Footwear heel design to allow natural movement of foot in heel andtoe/walking running.

Use of heel design to alleviate a medical condition of the foot,specifically shin splints/plantar fasciitis.

Cross reference to related applications: NA

In this paper shoe and footwear are used interchangeably.

Sagittal plane refers to the plane of the side view of the body, profileis also used with the same meaning.

Heel in reference to footwear means the ground contacting rear portionof an article of footwear, that portion which supports the heel of thewearer.

Ground refers to the surface being tread upon.

Stride cycle refers to the motions gone through by a foot and leg inbipedal locomotion, walking or running

BACKGROUND Field of Invention

This invention relates to the shape of the heel of footwear,specifically the shape and proportions of the elements of the heel ofthe footwear in the sagittal plane in relation to the rest of thearticle of footwear and the heel of the wearer. Said structure beingthat which does not interfere with (allows) the natural strike point ofthe heel in walking/running and allows the natural controlled fall(roll, declination . . . ) of the front of foot. Said structure does notcontribute to shin splints or plantar fasciitis by adding to the naturalforces exerted upon the foot and appending structures by increasing thelever arm of the wearer's heel.

Prior Art

Previously the design of the heel of has generally been done withattention to style, cushioning, and some specialties such as the heel ofa riding boot. Two medical problems have arisen. The first is known asMedial Tibial Stress Syndrome (MTSS), commonly called shin splints. Thebelow quote by the Mayo Clinic staff says:

Shin splints are caused by excessive force (overload) on the shinboneand the connective tissues that attach your muscles to the bone. Theoverload is often caused by specific athletic activities, such as:

Running downhill.

Running on a slanted or tilted surface.

Running in worn-out footwear.

Engaging in sports with frequent starts and stops, such as basketballand tennis.

Shin splints can also be caused by training errors, such as engaging ina running program with the “terrible toos”—running too hard, too fast orfor too long.

This is the generally accepted reasoning for the condition.

It is a fact that “Shin splints are caused by excessive force (overload)on the shinbone and the connective tissues that attach your muscles tothe bone.”

The reasons above following this statement could be contributors to theproblem. There is a more basic and more important element.

“Shin splints” refers to the condition of painful shins during and/orafter running or extended walking. The cause of this pain is damage tothe muscles and attachments of the anterior lower leg or shins as theyare commonly called. This is medically documented and will usually healif running is ceased. Why does this happen? It would seem running is anatural thing to do for survival at least if not for pleasure. The footis a highly functional, evolved, biomechanical device. It is welldocumented that persons living in areas of the world where they largelygo barefoot there is little incidence of shin splints, plantar fasciitisor other gait related pathologies or symptoms.

First to explain the functioning of a foot in the gait cycle in normalaction which would be bare foot. At the beginning of the heel-toe typegait cycle one lands on the ball of the heel FIG. 2, and the foot rollsforward over the round portion of the heel which is delineated by theradius of the calcaneus.

FIG. 1 point (7). This rolling motion disperses or spreads out some ofthe impact of the initial strike. It also allows a gradual loading fromthe first touch to full loading of body weight plus inertial forces. Inthis motion the anterior muscles of the shin control the attitude of thefoot—they hold the front of the foot up through their attachments to theupper anterior foot bones (22) against the weight acting on the heelthrough the fulcrum of the calcaneus (2)-talus (4) structure pivoting onthe talus (4)-tibia (6) joint. Point (12) is the approximate center ofrotation of the foot around the tibia joint. The front of the foot woulddrop with a shocking splat on impact if not suspended by the shinmuscles. This rolling action across the heel distributes the downwardforce of the body's weight while giving traction to the force generatedby the leg muscles to contribute to forward motion. The shin musclesalso act to absorb the shock of impact as they stretch with the force ofimpact. In actual heel strike walking or running there is not a greatdeal of movement of the foot in relation to the leg in the landingportion of the stride cycle. Under natural conditions the shin muscleshold the foot in place pulled up and under tension as the heel acceptsthe body weight being transferred from the opposite foot. This tensionrelaxes as the ball of the foot reaches the horizontal plane, and thefoot takes on full body weight and then prepares for the push offportion of the stride cycle.

Another important point in the cycle is that as the forefoot is closingwith the horizontal surface, the toes are drawn up as the forefootlowers in what is known as the Windlass mechanism. This is accomplishedby muscles in the shin area as well. This pulling up of the toestightens the plantar fascia (25) by pulling those tendinous tissuesaround the head of the metatarsals (26) in a manner somewhat like an oldfashioned windlass. This pulls directly at the fascia anchor point (24)on the medial process of the tuberosity or posterior portion of thecalcaneus just in front of the weight bearing ball shape. The tighteningof the fascia draws up and tightens the arch of the foot in preparationto accept full body weight. This happens as the knee moves over the footand full body weight is applied. The foot takes the weight, the shinmuscles relax and the foot flattens and begins to transfer to the pushoff position. The plantar connection with the forefoot is a majorstabilizer of the calcaneus bone, which is bearing the weight of thebody plus inertial forces.

It can be seen that in the landing portion of the stride cycle themuscles of the anterior portion of the lower leg do a dual function ofsuspending the forefoot under load and providing the tension tostabilize the arch of the foot and the calcaneus through the plantarfasciae. With each step the anterior or shin muscles are heavily loaded.

As can be seen in FIG. 2 when the foot first contacts at point (16)there is a given ratio of leverage between the attachment area of theshin muscles (11) and the area of the calcaneus that the contact forcesact on, (7). (Point 8 is a radius delineated by the calcaneus and abouthalf the distance between the calcaneus and the outer non-weight-bearingheel. It represents the moving point of contact of the outer heel, whichis compressed by body weight in landing. 50% is an estimated average ofheel pad compression under weight.) As the foot rolls forward on theround portion of the heel (barefoot) the leverage against the shinmuscles decreases. The contact point moves forward to point 14 where thecurve of the heel meets the horizontal and the foot is ready to acceptfull body weight. This means that as the body weight borne by theleading foot increases (the weight of the body is transferred to thefront foot as it moves forward over the foot) the leverage against theshin muscles decreases. Another way in which the leverage is decreasedin heel strike running/walking is that in taking a stride the forefootis naturally lifted, to prepare for contact, pivoting the front of thefoot upward in relation to the leg which in turn moves the heel downwardand forward. This forward movement of the ankle shortens the lever armlines (12-16, 17) at the time the foot first contacts giving a greaterlever advantage to the shin muscles. FIG. 2, point (17) shows the leverextension of a bare foot contacting at a 45° angle. This is near themaximum inclination and at this inclination the foot would not besupporting much of the body weight, as it would be too far out in front.These are significant changes in lever advantage and are very importantas the heel can be subject to forces of 3-4 times body weight oncontact. The action of running and walking at length is a highlyrepetitive action. Any imbalance in forces acting on the foot isrepeated possibly thousands of times in a given period of activity.

The aforesaid illustrates a workable system any footwear device shouldendeavor to complement. This means the optimum design for a shoe heelwould be a shape closely duplicating the contact area of a barefoot withits point of contact corresponding to that of the bare foot of thewearer. The rounded heel takes advantage of the lessening lever arm.However any placement of the contact point near optimum will result inmuch less strain on the shin muscles.

So why does a natural motion like running or extended walking for someresult in damage and pain in the shin muscles, connective tissue andbone? One of the only workable but not necessarily practical handlings,in running, for shin splints is to run barefoot. Another is to increasethe strength of the shin muscles, another to learn to run landing onlyon the forefoot. Shoes have been designed to ensure landing only on theforefoot. Barefoot style shoes that fit closely to the foot have beenfound to help. These solutions work for some but the general populacewants to be able to walk or run in a normal fashion and needs and wantscushioning and protection in a shoe.

If walking and running barefoot do not generally cause shin splints itfollows that there is a problem with shoes. Almost all running andwalking shoes extend the heel rearward. It is customary for the heel ofthe shoe to extend downward from a point at the back of the wearer'sheel plus the thickness of the shoe material often plus the welting. SeeFIG. 3A. Many designs of shoes extend even further rearward. Even whenthe heel of the shoe is not extended rearward the strike point is movedrearward by the cushioning of the sole of the shoe. The strike point isfar back of where the bare foot would strike.

In FIG. 3A, line 11-12 represents the lever arm the shin muscles pullagainst. Line (12-18) represents the counter lever arm of the calcaneus,which has body weight acting on it through the tibia talus joint. Line(16-18) represents the extension of lever arm caused by the heel of theshoe. This violates the natural amount of leverage the shin muscles workagainst when suspending and lowering the foot. It can easily be seenthat the leverage working against the shin muscles in this shoe isnearly doubled and this is not at all an extreme example. Shoes andboots that extend rearward much more are common. According to expertsthe forces on impact can be 3-4 times (another ref says up to 11×) bodyweight. Extend the strike point of the heel rearward and the leverageratio against the shin muscles is increased. The fairly conservativeextension of the heel in FIG. 3A increases the lever arm by almost 90%,almost doubling forces. A 200 pounder will go from 600-800 pound impactforce to something approaching a ton. The shin muscles are overpoweredand forced to extend by the impact and are damaged as a result. This ismost pronounced in activities like running or extended periods ofwalking where the repetitive action eventually damages the muscles andtendons of the shin area (bone damage can also occur from repetitivestrain on the tendon attachments). People who land heavily or areoverweight will suffer more from tendon strain.

An easy way to discover for yourself how this works is to put your barefoot out in front, toes up like you'd be landing on it while taking astride. Push on your heel with your weight and feel the pull on themuscles of the shins. Next, put on your shoes and do the same action andfeel the difference. You will feel the greatly increased pull on thoseshin muscles especially if body weight is applied as the forefoot nearsthe ground. They may not have the strength to hold the toes up.

FIGS. 3A to 8A give examples of prior art that show this extension ofthe lever arm over that which occurs naturally. It is this increase ofleverage against the foot structure that causes the slapping or clompingsound of a walking shoe or boot that is often heard when the forefootstrikes the ground/floor hard. This is because of the shin muscles beingover powered and the forefoot falling in an uncontrolled manner. Thisoverpowering of the shin musculature is what causes the damage to them.This is noticeable shoes or boots with heels of poor design and hardsoles. The sound is not heard so much in softer soled shoes but thedamage to the body is still going on.

To increase cushioning the clearance between the foot and the sole mustbe increased. It is the function of cushioning to gradually deceleratethe foot to remove the shock of a sudden stop of the foot hitting a hardsurface. To have a more gradual deceleration the thickness of thecushion must be increased to have a greater range in which to accomplishthe deceleration.

Any shoe design that raises the heel of the wearer needs to have thepoint of heel strike adjusted as any increase in height begins to movethe strike point rearward of the natural strike point. Even barefoottype shoes with minimal thickness still make small additions to thedimensions and thereby to the lever arm of the actual bare foot. Thewear layer of even this minimal type of shoe will extend the strikepointof the heel rearward by its thickness—a consideration for the seriousrunner. In a design where the contact point is relatively square as inFIG. 3A the pivot point is maintained at the point of contact ratherthan moving forward as in a rounded heel. This makes for the worst leverdisadvantage.

PROBLEM 2: Millions of runners and walkers suffer from plantarfasciitis. For some it is controllable, for many it prohibits them fromwalking, running or even enjoying life without pain. Plantar fasciitisinvolves pain and inflammation of a thick band of tissue and itsconnective points, called the plantar fascia, that runs across thebottom of the foot and connects the heel bone to the toes, FIG. 1 (24,25). Its function is to help stabilize the bones of the foot. As onetakes a step the toes are raised which tightens the fascia by pulling itaround the head of the metatarsal bones (26) in what is called the“Windlass effect”. This pulls up the arch of the foot (also referred toas a truss) readying it to take the body's weight. This not onlystabilizes the foot but is another part of the system to graduallyaccept the load while using the muscles and tendinous tissues to absorbshock. This cycle occurs as the forefoot touches down and graduallyloads as the knee passes over the foot and allows full transfer of thebody's weight.

The plantar fascia spans the five metatarsals and attaches to a singlepoint (24) on the calcaneus. In fact it is the plantar fascia that playsa major part in holding the calcaneus in place as it bears load. Anextended lever arm acting on the calcaneus, caused by shoe heel designwill overload the plantar fascia. Most of the problems and pain inplantar fasciitis involve the attachment of the fascia to the anteriorcalcaneus, point (24). Heel spurs are a common malady. This is the focalpoint of all the loading of impact. The shin muscles suspend the frontof the foot and toes. The plantar fascia connects this pulling force tothe calcaneus.

This overloading of the calcaneus on the crucial point of contactlessens the stability of the foot structure and increases the likelihoodof stride patterns deviating from the norm. Problems with weaknesses instructure will be magnified.

Another point which ties these two problems together is that the musclesworking to pull the toes up in the “windlass effect are anterior shinmuscles. Here again is direct increased strain on those muscles throughthe plantar fasciae when the strikepoint of the heel is extendedrearward.

There is a plethora of data available on how pronation, supranation,improper arch heights and so on affect gait and structure. It is easy tosee how these conditions can be exacerbated by overcoming the stabilityof the foot at the beginning of the cycle with an over-leveraged heelstrike. The arch itself is supported by the plantar fasciae, which inturn are acted upon by the shin muscles.

It is plain to see that extending the lever arm of the heel willdirectly increase the forces acting on the plantar fascia.

Extending the lever arm of the calcaneus causes overloading whichdamages the fasciae, ligaments and their connections to the bones. It isalso notable that a large number of those suffering from plantarfasciitis are runners, those whose work involves walking and those whoare overweight. Extending the heel and increasing the forces acting onthe plantar fasciae of an overweight person greatly increases theprobability of damage. The repetitive action of running or extendedperiods of walking magnifies the problems caused by increased leverageon the calcaneus.

Prior Art FIGS. 3A through 8A give examples of the lever arm of thecalcaneus being increased by shoe heel design.

PRIOR ART

Many prior designs have mentioned reduction of shin splints in theirclaims. U.S. Pat. No. 5,694,706, Penka discloses a running shoe with theno heel, the object being to force the wearer to land on the forefootthus ensuring the anterior muscles are not loaded, the entire weightbeing handled by the calf muscles. This may be a viable system if onechooses to walk or run in this fashion. This invention obviates the heellanding by design and does not interfere with my design for that reason.

U.S. Pat. No. 6,131,309, John Walsh mentions a need to correct abnormalpronation which can cause trauma, such as shin splints. His invention isa suspended heel carriage which allows movement of the heel and adifferent type of shock absorption. It does not address the problem ofunnatural heel strike overloading the Medial tibial muscles and tissuesor plantar fasciae.

U.S. Pat. No. 4,155,180, Edward H Phillips—Roller Shoe, discloses adesign of continuously rounded (front to back) sole of running shoe. Hestates: the rearward portion of the shoe is curved upward . . . . Thisshape functions to relieve the runner of his tendency to land on hisheel . . . thereby relieving heel shock. This design may work butnecessitates a very thick rounded portion of shoe sole and is not thechoice of all. In this design the heel is still extended rearward sothat if one does land on the heel there will still be an overloading ofthe shin muscles as well as plantar fasciae.

U.S. Pat. No. 7,100,307, Footwear to enhance natural gait discloses adesign of shoe with a round heel. This patent does have a heel designsimilar to that laid out herein but per drawings the radius of heel isnot maintained but rather enlarged which moves the strikepoint rearward,increasing the lever moment against the shin muscles. This design is fora specific shoe as well and does not encompass all forms of footwear.The patent does not make any claim as to the radial design of heel inthe sagittal plane to reduce shin splints or plantar fasciitis.

US patent Rosa discloses a shoe with a somewhat similar heel design butdoes not follow the formula of maintaining the radius of the heel andstrikepoint of the bare foot. It in fact states the primary point ofcontact is on the rearmost part of the shoe which increases leverageagainst the shin musculature. It also does not make any claim ofreducing the incidence of shin splints or plantar fasciitis.

EP 2319344 A1 by Stanislas Rio claims the risks of development of knownrelated pathologies from the interaction of the foot heel and thefootwear are minimized. His design is for a heel suspension and the heelof his design is conventional.

SUMMARY OF THE INVENTION

This invention has to do only with the rear part of the heel of anarticle of footwear which is the primary engaging unit in heel strikewalking/running The object of this shape of heel is to obviate thepossibility of unusual shin muscle/ligament strain and plantar fasciaestrain by maintaining the natural strike point of the heel of a barefoot. By maintaining the natural strikepoint, the lever arm of the heeland thus the loading is not increased.

This shape is only addressed in the sagittal view—that is fore and aft.This point is below the curve of the calcaneus bone at the approximatepoint it meets a parallel of the bottom of the foot as in FIG.

1 point (14) and following the radius of the contact area (8), rearwardon inclination.

This is the radius the heel follows under weight. This radius is definedby the radius of the calcaneus (7).

DRAWINGS—FIGURES

FIG. 1 shows a sagittal view of a bare foot on a horizontal surface,bearing weight.

FIG. 2 shows a sagittal view bare foot, inclined and contacting thehorizontal at approximately 20. FIG. 3A shows sagittal view of a footwithin a shoe, inclined and contacting the horizontal plane.

FIG. 3B is the shoe of FIG. 3A with a modified heel and is the preferredshape.

FIG. 3C is the shoe of FIG. 3A with an example of another type ofmodified heel. FIG. 3D is the shoe of FIG. 3A with a third type ofmodified heel.

FIG. 4A shows sagittal view of a foot within a running style shoe,inclined and contacting the horizontal plane.

FIG. 4B is the shoe of FIG. 4 with a modified heel.

FIG. 4B1 is the shoe of FIG. 4b with a plate to maintain the preferredcontact point when using a deformable resilient material.

FIG. 4B2 is views of inserts to maintain the preferred contact pointwith use of resilient materials.

FIG. 5A-8A show sagittal views of a foot within a shoe, inclined andcontacting the horizontal plane.

FIG. 5B-8B show sagittal views of a foot within a shoe with a heelmodified per

DETAILED DESCRIPTION—FIRST EMBODIMENT

FIG. 5C is the shoe of 5B with a lower heel.

FIG. 6C shows a variation of 6B which conforms with alternativeembodiment 3C.

FIG. 8C is an alternative embodiment of 8B.

FIG. 9 shows an example of a heel in which the contact point can beadjusted forward to reduce loading on foot and appended structure in thecase of weakness or pathology.

DRAWINGS—REFERENCE NUMERALS

2. the calcaneus bone.

4. the talus bone

6. the tibia bone

7. the radius of the calcaneus which delineates the form of the heel.

8. the radius of the contact area which is the radius the heel followsunder weight. This is approximately half the unloaded tissue thickness.

9. the radius of the contact area the heel follows under weightduplicated in the heel of the shoe.

10. radius 7 extended into a circle to illustrate the use of the back offoot as a marker for the placement of radius 9 in the shoe heel.

11. represents the approximate point on the top of the foot the shinmuscles pull on—shows the point of leverage of the shin muscles.

12. the approximate point the foot pivots on.

14. the contact point of the heel when the forefoot has touched thehorizontal. This point varies with thickness of heel tissue and shoematerial but is always perpendicular to this point and is a point online 14.

15. the contact point of a heel moved anterior for the purpose oflessening the load on foot structure in the case of pathology thereof.

16. the approximate contact point of the heel of a foot inclined inrelation to the horizontal. About 20° in FIG. 2.

17. the point of contact of the foot were it to contact the horizontalat 45°.

18. the contact point of the extended heel of the shoe.

Line 11-12 represents the approximate lever arm of the shin muscles.

Line 12-14 represents the approximate lever arm of the calcaneus-talusunder load which is pulling against the shin muscles and the plantarfasciae as the foot comes to rest.

Line 12-16 represents the approximate lever arm of the calcaneus-taluswhen the foot is contacting at an angle of 20° to the horizontal.

Line 12-17 represents the approximate lever arm of the calcaneus-talusif the foot were to contact at an angle of 45° to the horizontal.

Line 12-18 represents the approximate lever arm of the calcaneus-taluswhen the foot is contacting through the extended heel of the shoe.

Line 16-18 represents the addition to the natural lever arm applied bythe shoe heel.

Line 14-18 represents the addition to the natural lever arm applied bythe shoe heel as the forefoot contacts.

20. represents the horizontal plane or ground.

21. adjustable portion of shoe heel.

22. slotted area to allow adjustment.

23. screw fasteners.

24. attachment area of the plantar fasciae to the calcaneus.

25. the plantar fasciae.

26. head of the first metatarsal.

27. the rear profile of the heel of FIG. 3D.

28. represents the approximate area the shin muscles pull on to raisethe forefoot.

35. represents the horizontal (ground) if the heel meets it at a 35°angle.

40. represents the horizontal (ground) if the heel meets it at a 35°angle.

45. represents the horizontal (ground) if the heel meets it at a 45°angle.

46. represents a plate for insertion into the layers of the shoe solefor the purpose of maintaining the preferred contact point with use ofresilient shock absorbing materials in the sole.

46 a. is a posterior view of the plate shown with layers of resilientmaterials attached.

47. represents a layer of resilient shock absorbing material bonded tothe plate.

47 a. shows the form of the rearmost part of the resilient shockabsorbing material from the side view.

48. represents an optional wear layer bonded to the resilient material.

49. indicates the area of the concavity of the heel plate whereinadditional resilient material provides further cushioning.

50. represents a solid block for insertion into the layers of the shoeheel for the purpose of maintaining the preferred contact point with useof resilient shock absorbing materials in the sole.

Detailed Description—First Embodiment—FIGS. 3B, 4B, 5B, 6B, 7B, 8BPreferred Embodiment/Mode

All embodiments of this design deal only with the shape of the heel inthe sagittal plane that is, the side or profile view.

As seen in FIG. 1 the contact point of the radius of the heel when thefoot is flat on a surface is point (14). This point is defined as theapproximate point being vertically below the point where the lowerposterior radius of the calcaneus (7) meets a parallel to the horizontalplane of a foot supporting weight on heel and forefoot. This point ofthe calcaneus meets the surface through the padding of the heel tissuesand bears the weight of the standing body bearing on the heel.

As seen in FIG. 2 the contact point of the foot when it meets the groundsurface at an angle is described by radius (8). This is the radius ofthe contact area, which is the curve the heel follows under weight. Thiscurve ends at line 14. This curve or radius is approximately half theunloaded tissue thickness. This can also be described as the radius ofthe calcaneus plus approximately half the thickness of the heel tissue.A workable measure for this radius is approximately 14% of the totalfoot length. This radius can be positioned on the shoe heel by using aperpendicular aligned 0-2% anterior to the posterior most portion of thewearer's foot. This is given as a range because of differences inindividual person's heels. It is also fine tuning in comparison to thegross additional leverage caused by most shoes prior to this design.

This radius is brought down perpendicularly to the ground plane untilits lower part meets the intersection of line 14 with the bottomhorizontal plane of the shoe heel.

This can be further refined by using the intersection of this radius (9)with a 45° plane as in FIG. 3B, line (45).

The 45° line from this intersection to the welt area of the shoe can beused as the demarcation line of the rear of the shoe heel, giving morespace for material in the welt area. Material anterior to the 45° linewill not increase leverage against the heel. This also gives a cleanline to the back of the shoe for esthetic considerations. The 45° angleis chosen as the likely limit of inclination of the foot on contact. Itis well beyond the average but there are some that walk or run in thismanner.

A further definition of this shape of shoe heel is that no materialshall extend posteriorly from the area described by the lower part ofthe radius and above the intersection of the radius and the 45° angle bythat angle. This prohibition ensures no added leverage is applied to thewearer's heel by ground contact of the heel of the footwear. Thisdefinition can be changed to suit the chosen maximum angle of contactwhere it is determined that the maximum angle of contact will bedifferent for shoes intended for a given activity. For example a joggingor walking shoe or one intended for someone with pathology could have alesser maximum angle of contact. A shoe for certain sport activities mayneed a greater maximum angle of contact.

A heel of this design can be constructed with any of the variousmaterials used in heel construction. The only requisite being thatresilient type materials be of sufficient firmness or of a design toresist excessive deformation on contact that would move the contactpoint more than 1-2% of the entire foot length forward of thatdesignated by point 14. If the resilient material is not capable ofholding the preferred shape the heel of the shoe must have some built inmeans of maintaining that shape.

In a shoe intended only for running the wherein the contact angle withthe ground is near 0° the resilient material of the sole can be formedin the preferred shape. The shoe will not be suitable for walking asdeformation of the resilient material will move the contact pointforward in walking causing some jolting upon landing. If a fluid such asair or gel is used as part of the cushioning its confining structuremust be such that will not allow deforming of the given design thuspreventing the movement of the contact point forward or aft of thatdesignated. These requisites are well within the knowledge and abilitiesof anyone knowledgeable in the art of modern shoe making andmanufacture. Moving the contact point significantly forward of point 14will bring the foot into a condition wherein the shin muscles having alever advantage will momentarily halt the normal declination of thefoot. This will cause a jolt, which is transmitted up the leg. Furtheras the body weight passes over the foot the shin muscles will then beoverpowered and the foot will drop uncontrolled. Maintaining point 14 asthe final contact point is the most important point in maintainingnatural loading.

This design will work well with materials of little or no resiliencesuch as the relatively solid heel of a boot or service shoe or dressshoe.

The design can be incorporated into attached or molded heels.

The point of contact and the radius of the contact area may be finetuned to meet the exact needs of the wearer, for example in a shoe ofone who does a lot of running or one who has some pathology orabnormality of the foot.

Each shoe in FIGS. 3B, 4B&B1, 5B&C, 6B&C, 7B, 8B show examples of thepreferred radial or rounded design.

Operation—First Embodiment—FIGS. 3B, 4B&B1, 5B&C, 6B&C, 7B, 8B PreferredEmbodiment/Mode

The point of final contact of the contact radius has been placeddirectly beneath point 14 and is defined as being that point of theradius of the calcaneus which meets with a horizontal plane parallel tothat plane shared by the heel and forefoot of a weight bearing foot. Aworkable average measure is about 12% of the entire length of the footforward of the rearmost part of the heel as shown in FIG. 1. Making theheel of the shoe match the shape of the actual heel under load FIG. 1,radius (8) gives the best match to the natural strike zone of a barefoot. (Note: the center point of the calcaneus and the heel radius underload is forward of point (14) see circle (10). This is an importantpoint in bringing the radius down in the shoe heel so that it is notplaced too far back, as would be the case if the radius were alignedwith the center perpendicular to point 14. If the radius of the wearer's(person's) heel under load is extended into a full circle (10) it can beseen to closely align with a perpendicular, generally about 0-2% ofentire foot length forward of the back of the wearer's heel, FIG. 1.This makes that perpendicular a useful orientation point in aligning theradius on the shoe heel.)

Use of a round contact area provides a more gradual loading. This alsohas the effect of dissipating forces over a larger area. The result ofplacing the contact point in this manner is no excess strain on theshins, no excess loading of the plantar fascia and a very nice lightnessand smoothness to the impact of each step. This keeps all the forcesgenerated by the heel strike landing in a range the body is naturallydesigned to cope with.

Use of the round contact area also allows the use of more material whichwill tend to hold the given shape better under load so that the contactpoint is not moved forward of point 14 under load.

As seen in FIG. 6B and 6C the design is easily applied to a heightenedheel.

As seen in FIG. 5C the design works with a relatively low heel as well.With a low heel it is especially important to ensure the rear welt areais free of material that could contact the ground on heel strike.

Use of a resilient material for the purpose of shock absorption requiresthe maintaining of the preferred shape of the shoe heel as describedabove. Under load a resilient material will deform greatly, moving thepreferred point of contact—forward if the above shape is formed into theresilient heel. There are few ways to address this:

A molded shoe design wherein the lowermost portion of the shoe heel areais rigid. The outer form of the shoe is formed in a shape to incorporatethe preferred contact point and all the shock absorbing material isinside under the wearer's heel. A molded shell shoe design has beenaccomplished by others. It needs only to have the preferred contactpoint of FIG. 3B-9 incorporated into the form of the heel.

A V type design as shown in FIG. 8A,B,C. wherein the movement ofabsorbing materials is contained within the V shape whether that Vportion acts as a hinge or a leaf spring and the lower leaf is shapedaccording to the preferred contact area or minimally point 14, the finalcontact point of the preferred contact area.

A rigid piece of the sagittal shape of the wearer's contact area of thecalcaneus (FIG. 1-7) positioned vertically below that of the wearer,said rigid piece being bonded to the sole of the shoe and the resilientshock absorbing material on upper and lower planes such that itsposition is fixed and unmoving in relation to the shoe and thus thewearer's foot. Said piece being covered by resilient shock absorbingmaterial. Said resilient material being of variable thickness andfirmness as suits the manufacturer but said material being of graduatedthickness, thinnest to thickest from point 9 of FIG. 3B to point 14.This is illustrated in FIG. 4B1 where 47 a represents the tapering ofthe resilient material as compared to the original radius 9. This beingto maintain the desired contact point as weight is transferred from therear foot to the leading foot from lightest weight transfer in theregion of point 9 to full weight at point 14—matching the rate ofdeformation to the weight being borne at each point. An alternativemethod to accomplish this is to use a lighter resilient material in thearea of point 9 if a different shape is desired.

One form of the rigid piece is shown in FIG. 4B2-50. In whatever shapeis chosen the rear curve must be maintained and positioned such that thepreferred contact is maintained when covered by resilient material.

The material used for the rigid piece may be of any suitable to themanufacture such as urethane plastics, metal, even wood as is used insome types of sandals and shoes.

A preferred method to maintain the preferred contact point with the useof a resilient layer as the lowermost portion and wear layer or with aflexible wear layer attached is to make the plate which reproduces theshape of the wearer's calcaneus of a concave shape thus allowing the useof further resilient material above the plate and below the wearer'sheel. This is shown In FIG. 4B1-46. The plate can be made of materialsresistant to deforming such as stainless steel sheet, or any of severalrigid type plastics such as PVC or thermoplastic urethane. The plate isbonded and or sewn into the welting area of the shoe or bonded betweenlayers of resilient layers forming the sole. The plate should not extendpast the area of the first metatarsals where the shoe needs to beflexible to allow the foot to bend naturally as the wearer pushes offfrom the forefoot. The plate can alternatively be thinned out to theextent that it will bend easily at this area and additionally provideprotection to the wearer from sharp objects as well as being made morestable in the body of the shoe.

The rigid plate is molded to fit the form of the foot in the manner of ashoe insert and an arch support could be formed in as well if sodesired. The plate must be thick enough to prevent deforming of the areadesigned to duplicate the rigid form of the calcaneus under full load.The concavity of the portion formed to accept the heel of the wearerwill by its somewhat semi-hemispherical shape contribute to thestiffness necessary to prevent deformation of the form. FIG. 4B2 shows arear view of one form of a shoe heel. This shape may be made to suit theindividual designer. Only the rearmost portion of the form of thesagittal view FIG. 46 must be maintained to maintain the preferredcontact area.

The resilient shock absorbing material may be of various typesEVA—ethylene vinyl acetate polymer, various foam rubber products orothers known to the industry.

It will be found that the stiffness of the plate will spread the load ofthe heel which has a small imprint area and tends to “punch” throughregular foam showing up in accelerated wear in the area directly underthe heel. This spreading of the load will allow for less thickness ofresilient material or the use of less dense material.

Detailed Description—Alternative Embodiment FIG. 3C.

One can simply use point 14 as the strikepoint as has been borne out intesting. FIG. 3C shows the shoe heel is simply cut off at point 14 asseen in the sagittal view.

Operation—Alternative Embodiment FIG. 3C.

This shape has been tested and has been found to give similar comfortand ease of stride with no strain on shin muscles. It will slightlyalter the natural loading cycle making it less gradual than with arounded heel. This could possibly cause more strain on certain musclesafter many strides as in distance running. It works fine with hardermaterials but likely not hold its shape as well with resilientmaterials. It is not an esthetic design and would likely look odd orsuspect to the average consumer. It would also be subject to wear movingthe contact point forward much more quickly. One could make almost anyshape work in this embodiment as long as it has point 14 as the contactpoint, has no material posterior to the 45° angle or chosen maximumangle and supports the weight of the wearer.

Detailed Description—Alternative Embodiment FIG. 3D.

FIG. 3D shows the shape of the rear of the shoe heel is simply astraight line from pt.14 to the welt area of the shoe (27) as seen inthe sagittal view. This design adheres to the rule of no materialposterior to that shown in FIG. 3B. The shape in this embodiment canalso be varied as long as it has point 14 as the contact point, has nomaterial posterior to the 45° angle or chosen maximum angle that willcontact the ground and supports the weight of the wearer.

Operation—Alternative Embodiment FIG. 3D

This shape has been tested and has been found to give similar comfortand ease of stride with no strain on shin muscles. This shape is acompromise between the round design of FIG. 3B and the square of FIG.3C. It gives similar advantages to the square cut design, will wearbetter, deform less with resilient materials and will look moreacceptable to the average consumer. It is extremely simple to shape,mold or cut.

Detailed Description—Alternative Embodiment FIG. 8B.

FIG. 8B shows a runner with a resilient shock absorbing member(s)between the upper outsole and a leaf member meeting with the supportingsurface (ground). The leaf and shock-absorbing member are curved inaccordance with the design at the rear, the curve beginning at pt. 14.The curve is cut short of the bottom of the shoe to allow compression ofthe shock-absorbing member. The bottom member can also be formed assimply as ending its length at point 14.

Operation—Alternative Embodiment FIG. 8B.

This design gives the same advantages of maintaining the contact area ofa bare foot that is given by the round heels of the 3B-7B series whileallowing the use of cylindrical shock absorbing members. Theseshock-absorbing members could also be replaced by coil springs, wavesprings of a similar size. This particular design would have 2 shockabsorbing elements side by side. Only one is seen in the sagittal view.A similar design could be made with a single or pluralities of shockabsorbing member and or spring(s). The area between the leaves of the Vshape could alternatively be completely filled with resilient materialor various formations of sections of resilient/spring material invarious forms which allow compression while providing absorption ofshocks and with the possibility of energy return.

This design may also be formed of a leaf spring, which forms the lowerleaf and is incorporated into the upper outsole, FIG. 8C. Said leafspring design could also incorporate any of the shock absorbing and coilsprings elements described above.

Detailed Description—Alternative Embodiment FIG. 9

As it is the musculature of the shin area that suspends the forefoot andtakes up some of the force of impact as well as controlling the fall ofthe foot, it may be found that for therapeutic purposes in cases ofweakened or damaged musculature the strike point may be adjusted forwardof the natural point to compensate for such weaknesses. That is a heelcontact point formed anterior to point (14) or a heel with an adjustablecontact point that can be designed to adjust for that purpose. Thuseffectively shortening the lever arm of the heel of the wearer. This maybe applied to Plantar fasciitis and related conditions as well.

Operation—Alternative Embodiment FIG. 9

This moving of the contact point forward can be attained by simplycutting or molding a special shoe heel with the contact point movedforward to a degree suited to the individual.

A variation of adjustable strike point heel can be made in which thestrike point is adjustable for the exact need of a particular person andthen moved rearward toward the natural strikepoint as that person'spathology reduces. Thus allowing the structure of the foot to graduallystrengthen and attain normal function.

In FIG. 9 the lower portion of the shoe heel is a formed as a separatepiece (21). It is attached to the main body of the shoe by screws (23)which are located in slotted channels (22) to allow adjustment forwardand back. This allows the main contact point, (14 a when moved), to beadjusted forward of the normal strikepoint (14).

In adjusting the strikepoint forward it is necessary to adhere to therule of no material projecting to the rear which will increase heelleverage at any point of the heel strike. In designing this heel and theshoe it may be determined that one who has a foot pathology may not needthe room for a great deal of inclination on contact. For example aperson with chronic shin splints may only need a maximum inclination of30° on heel strike which will allow more clearance for material at therear of the shoe.

CONCLUSIONS, RAMIFICATIONS AND SCOPE

The reader will see that applying this design of shoe heel to anyfootwear design will allow the wearer the advantages of cushioning,protection and esthetics given by footwear without the damaging effectsof poor heel design. If one considers the size and weight of a body incomparison to the size and structure of the ankle and heel it is easy tosee that a small member carries a large load. This load is magnifiedgreatly in running As this structure has been formed over ages ofevolution it is therefore deemed of proper design by survival alone. Oneshould take great care before introducing modifications to the operationof the foot.

FIG. 2 shows the lever arms of the calcaneus and the supporting shinmuscles and FIG. 3A the extension of the calcaneus lever arm given by acommon shoe heel. It is very simple to see that any shoe heel thatextends this lever arm upsets a balanced system. This will result indamage to that system—minimally to the shin muscles, the plantar fasciaeand their attachments.

Maintaining the natural contact radius of the heel as in FIG. 3B willnot upset the balance of the natural system and will not cause unduedamage to the components of that system. Just being relatively close indesign to that set out herein will keep most feet in a tolerable rangeof stress. This design can be applied to any footwear. The design allowsthe use of cushioning without changing foot leverage. Even a flip-flopsandal increases the leverage of the calcaneus structure by thethickness of the sole wrapping around the heel with each stride. Onecould even walk with grace in a platform boot if the heel were cut tothis design.

It is not contemplated that there is any material or type of heel orheel cushioning or suspension currently used that couldn't be used whileconforming to this design. In heightened heels the contact area of theheel need only conform with that set out herein and the same advantageswill be realized. No special manufacturing techniques are necessary,only the shapes of molds or cuts of material need be changed.

The wearer of footwear with this heel design will instantly realize anease of motion and gait similar to walking barefoot.

This improvement on design of a running shoe or walking shoe or boot forthat matter will prevent or greatly lessen the problem of shin splintsand or plantar fasciitis for most and alleviate the problem for thosewho already suffer from shin splints/plantar fasciitis. This concept canbe carried further to any other type of footwear. The more one walks themore important the point of heel strike becomes. Also the heavier theperson, the more important this point of correct leverage in footwear.

It is also an important consideration for one with any of the variousfoot pathologies. It would be proper to correct the strikepoint of theheel before addressing other foot and related pathologies. It is quitepossible that many other foot pathologies arise from the excess forcescaused by increased leverage on the heel at contact.

NB. The strikepoint is referred to as point 14. Radius 9 is thepreferred strikepoint.

This is the radius formed by the progression of the strikepoint fromfirst contact at the maximum inclination of that contact to the point itmeets the horizontal that being point 14. Radius 9 does extend thestrikepoint rearward as it comes into contact with the ground but thefoot does not support a great deal of weight during this part of thestride unless the person moves in a very clumsy manner in which case itis even more important to not extend the strikepoint rearward. It isimportant to understand that in a bare foot the contact point movesforward as the heel contacts and rolls forward until the foot is fullycontacting. This forward movement of the contact point increases thelever advantage of the supporting shin muscles as the body weight borneby the foot increases with forward motion. This allows the shin musclesto do their function of supporting and controlling the suspension of therear foot as well as absorbing some of the shock of impact. As long asthis natural progression of leverage is not interfered with a healthybody is not unduly plagued by shin splints.

14% of overall foot length as the radius of the heel is a workableestimate of a normal average. It could be slightly more or lessdepending on the individual. If one looks at the difference this makesin leverage it is seen to be minor when compared to the gross additionsto leverage caused by shoe heels that do not conform to the measures ofthe wearer's foot itself.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A shape/form in thesagittal plane of the posterior ground contacting portion of the heel offootwear in which the shape of said footwear heel will not causeunnatural strains of the foot and appending structures brought about byfootwear heel induced increases in leverage applied to the heel of thewearers foot in the sagittal plane comprising: (a) said heel ofpredetermined raised structure of which the rear ground contactingportion of said shape is formed in profile beginning at a point which isvertically aligned with the point of contact (FIG. 1, point 14) of theradius of the calcaneus of the wearer's foot with a horizontal planeparallel to the plantar surface of said prone, weight-bearing foot, and(b) said shape of heel of footwear is capable of bearing the weight andforces of the heel of the wearer and can be the primary contact point inheel strike type bipedal locomotion, and (c) said shape of heel offootwear being such that no portion of said heel or shoe structureextends posteriorly to the contact point (14) in a manner that willsignificantly add to the natural leverage of the wearer's heel bycontact with the ground at any point of the stride cycle.
 2. A preferredshape/form of heel of footwear of claim 1 comprising: (a) the shape oflower rear of said shoe heel approximately conforming to the shape of awearer's heel under load and aligning vertically with the wearer's heelsuch that the natural lever arm of the wearer's heel is unchangedthrough the surface contacting portion of the stride cycle, and (b) saidshape being further defined as the approximate radius of the calcaneusof the wearer plus the thickness of the heel tissue while compressed asin bearing the load of the body in a stride, and (c) said shape ofwearer's heel under load being brought down to the base of footwearheel, perpendicularly to the plane of the plantar aspect of the foot,merging with the underside horizontal plane of the footwear heel at line(14) so that said shape of wearer's heel under load in the saggital viewis reproduced in the heel of footwear under the wearer's heel (FIG. 3B,radius 9), and (d) said shape of footwear heel having no materialprojecting posteriorly of radius 9 which would alter the lever arm ofthe wearer's heel by contact with the ground while bearing load in thestride cycle and (e) said form of heel when using resilient shockabsorbing materials as a portion thereof contain some form of solidstructure such as shown in FIG. 4B2 capable of maintaining the overallshape of the preferred contact point/radius under load as inwalking/runningwhen said resilient material is not capable ofmaintaining the preferred contact shape.
 3. A shape/form of heel offootwear of claim 1 comprising: (a) A line in the sagittal view whichcontinues approximately from the designated contact point (14) at thebase of the shoe heel to the back of the shoe welt area such that itdoes not cross posteriorly a line of predetermined maximum angle ofcontact of the heel with the horizontal plane and drawn through saidpoint of contact.
 4. A shape/form of heel of footwear of claim 1comprising: (a) the heel of the footwear formed of separate elementssuch that the lower ground engaging element is of the form of a leafhinged by a flexible portion to the midsole/outsole below the generalarea of the arch of the foot, and (b) the upper plantar portion of saidshoe heel is supported beneath, variously by means of cylindrical orother shapes of resilient material or coil or wave spring or othersprings or combination(s) thereof, and (c) the rear portion of saidground engaging element is confined posteriorly by the limitationsdescribed in claim 1 and where its rear portion has an upturning portionsuch as a radius of the proportions and placement of that of the heeldescribed in claim 2 the rear upwardly turning portion is cut short (butnever shorter than point 14) to allow full upward movement of saidelement in shock absorbing/energy return motions.
 5. A shape/form ofheel of footwear of claim 1 comprising: (a) said heel of the footwearformed of a separate element consisting of a leaf spring of “V” shape,the point of the “V” acting as a hinge and situated below the generalarea of the arch of the foot, one section or arm of the “V” constitutingthe lower leaf member and the upper arm being affixed or formed to orinto the outer sole of the heel of the shoe such that the lower arm ofthe “V” contacts the ground, bends with weight and thereby absorbs shockand provides energy return, and (b) the rear portion of said groundengaging element is confined posteriorly by the limitations described inclaim 1 and where its rear portion has an upturning portion such as aradius of the proportions and placement of that of the heel described inclaim 2 the rear upwardly turning portion is cut short (but nevershorter than point 14) to allow full upward movement of said element inshock absorbing/energy return motions, and (c) said leaf spring may beadditionally equipped with shock absorbing or other spring elements, and(d) said leaf spring may be equipped with a stopper inserted into the“V” of the spring affixed to one leaf and coming in contact with thesecond leaf as it compresses under load. Said stopper being made eitherfrom solid or resilient material, the resilient material offering ashock absorption function. The stopper may be of varying shape such thatthe lever arm of the spring is changed as it compresses allowing anadjustable, progressive spring rate.
 6. A shape/form of heel of footwearof claim 1 comprising: (a) a heel of footwear with an adjustable pointof contact wherein the contact point is made able to be moved anteriorto that of claim 1 to shorten the lever arm acting against the wearer'sheel thereby providing a lessening of the loads to the foot andappending structures to give relief in the case of various types ofinjury or weakness in portion or portions of said structure such asmedial tibial muscles or plantar fascii, and (b) said shape continuesposteriorly to meet the rear welt area of the shoe in a manner such thatno portion of said heel structure will substantially add to the naturalleverage of the wearer's heel by contact with the ground at any point ofthe stride cycle, and (c) said shape being moved anteriorly by cutting,molding at manufacture or cutting or other various means of reshapingafter manufacture.
 7. A shape/form of heel of footwear of claim 6comprising: (a) a lower section of the heel which is formed separatelyfrom the main body of the heel such that it is able to be adjustedanteriorly and posteriorly, and (b) said section is affixed by variousmeans to the main body of the heel so it may be adjusted then fixed at asuitable setting, one means of affixing being screws through the movablesection into the main body of the heel with slotted channels in thelower movable section aligned sagittally to allow adjustment, and (c)the shape of the entire rear of the heel of the footwear including therear portion of the shoe is formed such that no material projectsposteriorly in a manner that it could increase leverage against the heelby contact with the ground at any portion of a normal stride cycle.